Gym memberships are something of a luxury these days. But without the usual suspects -- treadmills, elliptical trainers, cable machines and free weights -- is it easy to get a decent workout?

Absolutely. Just take your workout to the streets -- or the beach or the hiking trail.

Hiking trails with their hills and uneven terrain, are perfect places to practice interval training and improve cardiovascular endurance, as well as strengthen core and leg muscles.

Miles of beach, are a fitness boon. Muscles must work harder when feet dig into sand, ramping up the difficulty of even the easiest workouts.

And the concrete and steel structures all over cities provide the perfect way to challenge all major muscle groups while partaking of parkour, a relatively new discipline in which people use only the body to navigate the environment by scaling walls, vaulting ledges and jumping up stairs.

Even for those who haven't abandoned the gym, training outside presents a break from the monotony of machines and can improve performance in sports such as basketball, soccer, skiing and cycling.

Curious about the possibilities, we polled three fitness experts for L.A.-area workouts that provide great views and don't cost a thing. Sure, some exercises may seem familiar -- but doing them on an incline or an uneven or shifting surface adds an exhilarating element.

In some cases, we offer sets and repetitions for each exercise -- but they're only suggestions. Too easy? Increase the intensity of the exercise and add a few more reps. Too challenging? Knock down the energy and do a few less. Always work at a comfortable pace.

Most people associate the beach with swimming or surfing, but the water isn't the only exercise-friendly element. Many developed beach areas, also feature bars, rings, swings and balance beams -- free equipment that can make a workout engaging and fun. Plus, the sand offers a shifting surface that forces the stabilizing muscles of the core to fire. Feet sink in, making muscles work harder and creating a bigger calorie burn.

Jennifer Cohen ( www.jennifercohen.com), fitness trainer and author of "No Gym Required," showed a number of strength and aerobic training exercises that can be done on a warm day or even a brisk winter one. Beach pails act as weights when filled with wet or dry sand, adding an extra challenge. These exercises are also easily done at a park or a playground with similar equipment.

Ab crunches and pelvic tilt on a swing

Lie on the sand on your back with your feet in a swing seat, legs extended and hands behind your head. Contract the abdominal muscles, bringing the knees and the shoulders together without straining the neck. Release and repeat. This targets core muscles. For the pelvic tilt, place back and head on the sand, and feet on the swing seat with knees straight. Push the pelvis up and release, squeezing the glutes.

How many: Repeat both exercises about 15 times.

Decline push-ups on a balance beam

Push-ups on a decline (where hands are lower than feet) have an added degree of difficulty, since the body is working harder against gravity. Place hands in the sand and toes on top of a low balance beam (or, to make it a little easier, place them against the side of the beam) and, with hands shoulder-width apart, lower the chest to the ground as far as possible while keeping the body straight. This works the entire upper body and engages the core, which has to work even harder to stay stable since hands are on an uneven surface and digging into the sand.

To add even more difficulty, bring one knee toward the chest during the push-up, alternating legs. You can also switch between bent-leg and straight-leg push-ups. Not that much upper body strength? Switch things around and do an incline push-up, with hands on the beam, toes in the sand.

How many: Three sets of 10 to 12 reps.

Triceps dip on a balance beam

In the basic triceps-dip move, hands are placed on the beam, fingers forward. Knees are bent at a 90-degree angle and the body is lowered until the elbows also come to 90 degrees. Make sure your shoulders are relaxed and not hunched. "You can plateau on this very quickly," Cohen says, "so you always need to increase the resistance." To do that, straighten the legs and dig your heels into the sand, then lower elbows to 90 degrees. Or start with knees at 90 degrees again, but cross one leg over the other, then switch legs. For a really tough version that targets core muscles as well as the triceps, extend one leg and the opposite arm.

How many: Three sets of 8 to 10 reps.

Speed skating

Mimicking speed-skating moves works the legs and cardiovascular system. As with actual skating, outer thigh muscles get a workout, as do the torso and the arms. Stabilizing trunk muscles are engaged as well.

Starting in a standing position, move the right leg back and to the left side while leaning forward and touching the toe of the left foot with the right hand. Switch and repeat, keeping the body low to the ground. Doing this while lifting a weighted sand pail with the outstretched arm increases the difficulty; switch the pail from hand to hand while switching feet.

How many: Start with 30 seconds, then gradually increase the amount of time.

Crab walk

With chest facing up, place hands and feet in the sand. Walk backward or forward on all fours in a straight line at a comfortable pace, pushing off the heels, for about 20 to 30 feet, making sure not to drop the torso. The sand is the key element here, as it provides a significant resistance. This will work the triceps, hamstrings, quads, calves, glutes and core.

How many: Complete two lengths, moving forward or backward.

Plyometric jumps

Draw a 10- to 15-foot line in the sand, or stretch out a jump rope. Starting on one end, bend the knees and jump across the line, zigzagging back and forth. "Since your feet are planted in the sand," Cohen says, "it's harder to get power and height." Make sure to land in a squat position before jumping again to protect the knees and other joints. Explosive moves like these are great for sports such as basketball and volleyball but should be done only when the body is fully warmed up.

How many: Beginners should do about 10 to 15 jumps; more advanced exercisers can do two sets.

Pull-ups on rings

Find rings that are low enough to be reached without straining or jumping -- they should be about shoulder height or a little higher. Grab the rings with both hands, keeping the rings parallel, and gradually lower your body, legs straight, feet in the sand and slightly apart (the wider apart the feet are, the easier the exercise). Pull yourself up toward the rings, keeping the body straight, then go back down. This works shoulder, back, triceps and chest muscles. Doing this exercise with the rings turned 45 degrees also works the biceps.

How many: Three sets of 12 to 15 reps.

Inverted ab crunches on a bar

This move targets all the muscles of the abs, but it's an advanced exercise and should be done with a spotter. Find a bar low enough to swing your legs over, and carefully climb up so that your knees are folded over and you're hanging upside down. Gently lower your head and torso toward the ground, stretching the arms past the head. Contracting the abdominals, slowly move your torso up toward the bar, touch it with your hands, then slowly go back down, letting arms go past your head again. Note that hanging upside down may cause headaches or dizziness, so always proceed with caution.

This multi-part exercise incorporates cardio and full-body conditioning. Begin with feet hip-width apart and do small running steps in the sand for about 30 seconds. Drop to a squat, then, with hands in the sand, kick the legs out to a push-up position. From here, there are several options: Jump back into a squat position, stand up and repeat; do a push-up, squat, stand and repeat; or segue from the push-up position to side planks, return to push-up position, squat, stand and repeat. The more that's added on, the more difficult this exercise becomes.

How many: 10.

Workout 2: The trail full-body workout

Hiking trails are good for more than a challenging outdoor walk. The uneven terrain forces the body to use more stabilizing muscles in the abdominals and back, which improves balance and strengthens the core. Sprints or walking fast uphill puts you into an anaerobic zone, which taxes the muscles and benefits the cardiovascular system.

We took to some trails in California's San Gabriel Mountains foothills with Keli Roberts ( www.keliroberts.com), trainer and former IDEA Health & Fitness Assn. international instructor of the year. She demonstrated exercises that are perfectly suited to countless basic hiking trails. Though beginners can easily tackle these moves, it's important to pay attention to the modifications and make sure the terrain isn't excessively rocky or craggy, because it's easy to slip on loose rocks and dirt. Always keep an eye on the ground while moving. And stay focused on the task at hand. Take in the view on a break -- and gaze at the rugged hillsides and wildlife when stopped, not during an exercise that requires concentration.

First, warm up: Walk briskly, run or run-walk for 15 minutes, increasing speed as you go. Then try:

Hill skip repeats

The hill skip is an exaggerated skipping movement in which the knee and opposite arm drive up as high as possible during the jumping portion. Go for height, not distance, Roberts says. Done on an incline, the skip is a plyometric (high-intensity, explosive motion) and anaerobic move that develops strength and speed. It also targets the calves, glutes, hamstrings and quads, and some shoulder and latissimus dorsi (lat) muscles. Core muscles are also affected, as the body strives for balance.

"This helps develop the ability to lift yourself up," Roberts says. "It makes running or playing soccer or going up a flight of stairs much easier. It's like putting steroids in your hike."

How many: Five to 10 repetitions, with about a minute-long walk down the hill inbetween to recover.

Uphill walking lunges

Take walking lunges out of the gym and put them on a hill and suddenly this already challenging exercise becomes super-tough. "It's a complete exercise for the lower body," Roberts says, targeting hamstrings, quads, glutes and inner thighs. It conditions the ankles and feet when the body tries to right itself on an uneven surface.

In the lunge position, keep knees at a 90-degree angle, and don't rush the movement -- take a second or two to stabilize the body before pushing off. Pumping the arms helps engage more core muscles.

How many: One to three sets of 20 paces each with a one- to two-minute rest between sets.

Hill sprints

Repeated sprints uphill followed by rest periods improve cardio function and work the leg muscles. Choose a navigable path about 50 meters (164 feet) long from the flat to the crest of the hill. Go for maximum speed, pumping the arms as you go. Walk down the hill to recover completely -- about two minutes -- before sprinting again. Once you feel yourself flagging during the run, stop: This is about quality, Roberts says, not quantity.

How many: Varies depending on ability, but no more than 10.

Incline push-ups

These are easier than regular push-ups but still provide good upper-body conditioning. Find a sloping wall or embankment and place both hands on the wall at shoulder height. Lower your chest toward your hands, keeping elbows out and the body in alignment from head to toe -- don't push hips out, or stomach in. This move works triceps, upper back, shoulder and chest muscles, and abdominals. Lifting one leg during the movement destabilizes the body, engaging more of the core.

How many: Two sets of eight to 15 reps. (Try alternating with sets of walking lunges.)

Double-leg stretch

This core-strengthening move borrows from Pilates and can be done on top of a picnic table, flat bench or flat rock. Begin by lying down face up, arms and legs tucked in toward the torso. Extend arms and legs out at the same time, keeping them off the table -- the lower they are, the tougher this exercise becomes. Exhale on the extension, then inhale as the arms and legs are brought in. The head and neck are lifted but not strained -- beginners can keep their head on the table. The trunk is held still during the movement, and all core muscles in the abdomen and back are engaged.

How many: One to two sets of 10 to 15 reps.

Interval runs, or fartleks

Don't giggle. Fartlek is Swedish for "speed play" and refers to alternating short periods of high- and low-intensity aerobic conditioning -- without a break -- to improve the cardiovascular system. Roberts recommends switching between one minute of fast running followed by one minute of slow running or even walking (beginners can alternate between fast and slow bouts of walking). "This is a great drill that makes you a much faster runner," she says. On the downhills, Roberts suggests trying to keep the same pace, going with gravity.

How much: Run or walk as long as possible, cutting back on the overall time if adding in other exercises on the trail.

Uphill lateral traveling squats

Up the ante on this popular exercise by traveling sideways on a hill. This engages major leg muscles, including inner and outer thigh muscles and glutes.

Keep knees at 90 degrees in the squat position, feet shoulder-width apart, and hold hands in front. Work your way upward, using the top leg to pull you up the hill rather than pushing off from the bottom leg. As with lunges, take time to steady the body while in the squat. Walk down the hill to recover, then repeat.

How many: Two sets of 20 paces.

Star balance

This exercise may look simple, but core strength and balance are required to pull it off. Find a gently sloping tree trunk or wall on which to place one hand, then (keeping the arm straight) lift the outside leg without bringing up the hip. Raise the other arm up into a star position while leaning into the tree. Beginners should lift the arm and leg only as high as possible while keeping the body balanced. This drill engages oblique (side) muscles of the trunk as well as glutes, and improves balance.

How many: Hold one side 40 to 60 seconds, then repeat on the other side.

Step-ups

This exercise can be done on a park or picnic table bench, a firm embankment or a large, flat rock. When one foot is placed on the bench, the knee should be at a 90-degree angle.

Step up on the bench with the right leg and bend the left leg, pointing the knee forward,so the left foot is touching the right knee. This works the glutes, hamstrings and quadriceps, and uses the inner and outer thigh muscles for stability. "Doing these makes everything you do easier -- climbing hills, walking up stairs," Roberts says. Rests between sets are allowed, but plowing through keeps the heart rate up and works the cardiovascular system harder.

In the noncompetitive discipline known as parkour, you move through the environment as efficiently as possible, using only the human body. Parkour, which originated in France and is becoming increasingly popular in the U.S., incorporates vaulting, jumping, skipping, climbing, running, hanging, swinging and other moves as participants proceed from one place to another. Enthusiasts are drawn to the broad navigational possibilities and challenges, with no rules and no set techniques.

Parkour does require a certain level of athleticism, and the more athletic one is, the easier (and more fun) it is to traverse the terrain, be it concrete or earth. Anyone starting from scratch may want to begin more traditional strength and cardio training before tackling parkour moves or while learning them. Upper-body strength is especially important for climbing walls and vaulting, while leg strength is paramount for jumps. Strong joints make for better landings, and good cardio function is necessary for moves that require endurance. Core strength is key since it's integral to almost every move. Balance and core strength are required for safe landings.

Parkour itself is excellent for training pretty much all the muscles of the body as well as building bone density.

The exercises here, demonstrated by Cliff Kravit, a parkour instructor (www.lagymnastics.com/index.php) and founder of PKCali (www.pkcali.com/news.php), an online resource for parkour in Southern California, are based on fundamental parkour moves. He showed off some of those moves at UCLA's building-dense landscape, taking advantage of the many stairways, walls and curbs. But they can be done anywhere there are stairs, ledges, walls, railings -- even trees. Try a downtown center or parks. Though urban locations offer fairly flat terrain, Kravit recommends wearing comfy clothes and shoes that allow for movement (tennis shoes or canvas flats might be easiest for beginners).

Some believe traceurs -- those who practice parkour -- are just thrill-seekers, but Kravit says that's not the case. Safety is vital, and progression is key -- you build on basic moves until proficiency is attained. Focus on the exercise before, during and after completing it; losing concentration can mean tripping, slipping or falling. Beginners should practice on flat ground whenever possible, gradually increasing the difficulty, and use a spotter when necessary.

There's no recommended number of sets or reps for each move; one's fitness level, Kravit says, will determine how many should be done. Always strive to maintain good form, and avoid fatigue that can lead to injury.

Cat vault, saut de chat, or Kong vault

This basic move entails leaping over a waist-high obstacle that has some depth to it and has a flat top -- a low wall, say. It's a quadrupedal movement (involving arms and legs), so both upper and lower body muscles are engaged.

To start, take a few running steps toward the obstacle, place both hands on the far end, tuck the legs and bring them through, using the momentum to jump over the wall. "You want to keep moving forward, and continue the momentum and fluidity," Kravit says, so keep running a bit after landing. To make this move easier, jump and stop on the top of the wall, knees bent, then jump down. Doing this a few times will work the cardiovascular system.

Step-up

This move is good preparation for climbing walls, which often requires a burst of speed and power to propel the body vertically. Step up on a flat, elevated surface, about one to 1 1/2 feet high, with the ball of the foot, then drive the body upward, hands reaching above the head, before landing on the ground, knees bent to absorb the impact. Beginners can try this without the jump. Repeat, then switch legs.

Box jump

Find a flat, wide surface on which you can jump comfortably, even if it's only six inches off the ground, like a low curb or stair. Bend the knees and jump up, landing on both feet, then immediately jump down and repeat. "It should be a quick re-bound," says Kravit. If going up and down that quickly is too difficult, try adding an extra hop while on the ground; this will also help stabilize the body. Leg and core muscles are engaged, and this exercise also trains fast-twitch muscle fibers, which are needed for quick bursts of speed or strength, and are important in jumps, a cornerstone of parkour.

Sideways quadrupedal stair exercise

Facing sideways on a flight of stairs, place hands on two consecutive steps and propel the legs upward, using the upper body, and lifting the feet up a couple of steps higher than the hands. This move targets upper-body muscles -- especially the lats -- and the core. Going down will be easier, but use the same method: Place the hands first, then propel the legs downward using the upper body to control the movement.

Cat balance

This is another quadrupedal movement that mimics the way a cat walks, and gives a full-body workout. On a low ledge or the ground (try to find a seam in the sidewalk), crouch on hands and feet, making sure the hips aren't elevated too high and the knees aren't touching the ground. Move backward and forward in a line, placing weight on arms and legs, keeping the head and neck aligned and always looking just ahead of the hands, which will help maintain balance.

"This gets you used to being horizontal and low to the ground," Kravit says. "It's about developing that center of balance, and [it] gets you used to moving the arms and legs in conjunction with one another."

Wall shimmy

Strong arm and back muscles are needed for this exercise. Find a wall from which you can hang without touching the ground. Grasp the top of the wall with both hands, and place the balls of the feet against the wall, bending the knees. Shift your body sideways along the wall, moving one hand and foot at the same time, then the other hand and foot. Mastering this move will make wall climbs easier, since it gets the body strong and stable for more advanced work.

Cat jump or Kong vault up stairs

This variation on the basic Kong vault uses stairs and is another quadrupedal movement. Starting in a crouch, push off with the legs, land the jump on the hands a few stairs up and then bring the feet up, landing on a stair lower than the hands. Use the upper body to absorb some of the impact of the jump so that the knees don't feel all of it. Continue up the stairs, but walk down -- do not do this exercise down the stairs.

Pick two points with some distance between them; beginners can practice on flat ground; those who are more advanced can choose a more elevated spot, such as a low curb or wall. Choose a spot on which to land, and starting in a squat position, jump and try to land on that exact spot, never taking your eyes off the mark. Use the arms to propel the body upward and strive for a full-body extension if making a long jump. Land on the balls of the feet with knees bent to absorb impact. Take a moment to find your center of balance before jumping again. This exercise works the legs and trains core muscles.